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91.
潜孔锤冲击作用下土体变形的有限元分析 总被引:1,自引:0,他引:1
潜孔锤冲击挤密钻进过程中周围土体的变形机理是一个高度非线性问题。针对潜孔锤在土中的面-面接触问题,运用Drucker-Prager屈服准则为判据,将土体视为DP材料,通过钻具与土之间的接触及施加冲击载荷来模拟钻进过程,从而建立了潜孔锤在土中冲击挤密钻进的有限元模型。利用非线性瞬态动力学有限元分析手段,对钻进过程中冲击力对土的作用加以研究,分析了钻具周围土体的应力、应变以及钻具与土体的摩擦情况。结果表明,在冲击载荷作用下,锥形钻头前端土体应力集中,并形成应力泡,冲击功主要用于竖向压缩土体,而水平方向的挤压作用相对较小,摩擦应力在钻头锥面附近出现峰值,是影响钻进速度的主要原因之一。 相似文献
92.
I. N. Ishchuk 《Measurement Techniques》2007,50(10):1081-1086
A three-dimensional solution of the direct problem of heat conduction when a linear pulsed heat source acts in the plane of
contact of two semibounded bodies is presented. The solution is obtained by the method of finite differences. An example of
the modeling is considered.
__________
Translated from Izmeritel’naya Tekhnika, No. 10, pp. 42–45, October, 2007. 相似文献
93.
94.
D. L. Cotrell A. J. Kearsley 《Journal of research of the National Institute of Standards and Technology》2007,112(3):153-161
In this work, optimal shaft shapes for flow in the annular space between a rotating shaft with axially-periodic radius and a fixed coaxial outer circular cylinder, are investigated. Axisymmetric steady flows in this geometry are determined by solving the full Navier-Stokes equations in the actual domain. A measure of the flow field, a weighted convex combination of the volume averaged square of the L2-norm of the velocity and vorticity vectors, is employed. It has been demonstrated that boundary shape can be used to influence the characteristics of the flow field, such as its velocity component distribution, kinetic energy, or even vorticity. This ability to influence flow fields through boundary shape may be employed to improve microfluidic mixing or, possibly, to minimize shear in biological applications. 相似文献
95.
96.
Ashraf Ayoub 《Computers & Structures》2003,81(7):411-421
This paper presents an inelastic element for the analysis of beams on foundations. The element is derived from a two-field mixed formulation with independent approximation of forces and displacements. The state determination algorithm for the implementation of the element in a general purpose nonlinear finite element analysis program is presented and its stability characteristics are discussed. Numerical studies are performed to compare the model with the classical displacement formulation. The studies confirm the superiority of the proposed model in describing the inelastic behavior of beams on foundations. 相似文献
97.
本文在重点考虑TiNi合金高弹性变形量的前提下,采用等向强化模型,对不锈钢和超弹TiNi合金在法向接触载荷作用下的六种模型进行了有限元(FEM)分析。结果表明:在相同载荷条件下,超弹TiNi合金产生的von Mises弹性应变要高于不锈钢,但其von Mises应力和塑性应变却恰恰相反,在同一载荷下该合金发生塑性变形的区域要小于不锈钢;此外,超弹TiNi合金发生塑性变形要比不锈钢困难,所需的临界载荷值随其最大弹性变形量(屈服点处的应变值)的增加而增加。最后,基于本文的有限元计算结果对超弹TiNi合金的蘑粒磨损和疲劳磨损机制进行了讨论。 相似文献
98.
P. PAPANIKOS K. I. TSERPES SP. PANTELAKIS 《Fatigue & Fracture of Engineering Materials & Structures》2003,26(1):37-47
A progressive fatigue damage model has been developed for predicting damage accumulation and life of carbon fibre‐reinforced plastics (CFRP) laminates with arbitrary geometry and stacking sequence subjected to constant amplitude cyclic loading. The model comprises the components of stress analysis, fatigue failure analysis and fatigue material property degradation. Stress analysis of the composite laminate was performed by creating a three‐dimensional finite element model in the ANSYS FE code. Fatigue failure analysis was performed by using a set of Hashin‐type failure criteria and the Ye‐delamination criterion. Two types of material property degradations on the basis of element stiffness and strength were applied: a sudden degradation because of sudden failure detected by the fatigue failure criteria and a gradual degradation because of the nature of cyclic loading, which is driven by the increased number of cycles. The gradual degradation of the composite material was modelled by using functions relating the residual stiffness and residual strength of the laminate to the number of cycles. All model components have been programmed in the ANSYS FE code in order to create a user‐friendly macro‐routine. The model has been applied in two different quasi‐isotropic CFRP laminates subjected to tension–compression (T–C) fatigue and the predictions of fatigue life and damage accumulation as a function of the number of cycles were compared with experimental data available in the literature. A very good agreement was obtained. 相似文献
99.
100.
采用新的小参数、将摄动法和有限元法相结合,研究了复合载荷作用下波纹管横向非线性弯曲的位移和应力分布。小参数为结构环向应变的均方根。将节点位移摄动展开,并以复合载荷的等效节点载荷为参考载荷,将其公共系数1摄动展开。由此划分载荷的级别、建立各级载荷和相应位移的关系,避免了常规的迭代运算。算例为一考虑自重的U型波纹管在注满水时的横向非线性弯曲问题。计算表明,波纹管的挠度和膜应力有非常显著的非线性效应;当最大挠度与壁厚之比达到5.1后本法将失效。本法在摄动小参数的选取和复合载荷的处理上有特色,能解决较大的挠度问题。 相似文献